Electric furnace and method of operation.



W. K. BOOTH.

ELECTRIC FURNACE AND METHOD OF OPERATION..

APPLICATION FILED JUNE 29. 1911.

1,244,415. Patented 061;. 23,1917.

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W. K. BOOTH.

ELECTRIC FURNACE AND METHOD OF OPERATION.

APPLICATION FILED JUNE 29. 1911.

1,244,415. Patented Oct. 23,1917.

UNITED STATES PATENT OFFICE.

WILLIAM K. BOOTH, OF CHICAGO. ILLINOIS. ASSIGNOR TO BOOTH-HALL COMPANY, OF CHICAGO. ILLINOIS. A CORPORATION OF ILLINOIS.

ELECTRIC FURNACE AND METHOD OF OPERATION.

Application filed June 29, 1917.

To all whom it may concern:

Be it known that I, IVILLIAM K. Boorn, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Electric Furnaces and Methods of Operation. of which the following is a specification.

This invention relates particularly to electric furnaces which operate normally by passing electric current between an upper electrode and a wall or hearth contact, and through the interposed charge which preferably is fused by the arcing of the electric current.

The primary object of the invention is to provide an electric furnace which can be put into operation with facility and which will operate efficiently. A further object is to provide an improved method of operating electric furnaces.

The accompanying drawings illustrate furnaces embodying the invention, operating on the single-phase, the two-phase, and the tri-phase systems.

In the drawings- Figure 1 is a diagrammatical view of a single-phase furnace embodying the invention; Fig. 2, a similar view of a two-phase furnace embodying the invention; Fig. 3, a similar View of a three-phase furnace embodying the invention; Fig. 4, a broken elevat-ional view of the furnace shown in Fig. 1, illustrating somewhat conventionally the automatically adjustable electrode employed; and Fig. 5, a similar view illustrating a manually adjustable auxiliary electrode employed.

Referring to Figs. 1, 4 and 5, illustrating the preferred form of single-phase furnace, A designates a melting chamber provided with refractory walls which may be formed of any suitable fire bricks or refractory ma terial, these Walls. or the hearth portion of the furnace, at-least, being of a material which. while virtually non-conductive when cold. becomes relatively conductive when hot B, a wall-contact embedded in the hearth near its inner surface. and preferably comprising an iron or steel grid filled with or embedded in a block of carbonaceous material; C. an automatically adjustable main electrode which depends from the roof or arch into the melting-chamber; D, a manu- Specification of Letters Patent.

Patented Oct. 23, 1917.

Serial No. 177,679.

ally adjustable, or withdrawable, auxiliary electrode, which depends into the melting chamber; E. the primary winding of a single-phase transformer; and F. the secondary winding of said transformer which has one terminal connected by a conductor G to the main electrode and the other terminal connected by conductors H and H to the wallcontact B and the auxiliary electrode D, respectively. As thus described, it will be understood that the wall-contact B and auxiliary electrode D are connected to one side of the secondary circuit and thus are of the same polarity, and the main electrode C is connected to the other side of the secondary circuit and is of opposite polarity; also, that the hearth provides a refractory facing, 1. for the wall-contact B, which facing becomes sufficiently conductive to carry the load only when the furnace is hot.

The furnace is shown provided with a charging door K and a tap-hole L. In the furnace is the charge M which is to be melted or reduced. In melting scrap-metals, for illustration, the preferred method of operation is to lower the auxiliary electrode D into contact with the charge and maintain an are between the main electrode C and the charge M, as at 2. The current passes, therefore. between the upper main electrode and the (upper) auxiliary electrode through the charge. The fused metal trickles to the hearth and collects at, M, thus heating the refractory facing 1 of the wall-contact B and establishing the main circuit through the hearth. After the preliminary heating operation, the auxiliary contact D is preferably withdrawn sufficiently to throw it wholly out of operation, and the load is then carried wholly through the wall-contact.

The invention enables the wall-contact to be used to secure good distribution and etlioiency and to avoid undue electrode complications. while still permitting the furnace to be preliminarily heated with the greatest facility. In a single-phase system. the use of but one automatically regulated electrode is required for automatically stabilized operation. and the duty placed upon the manually adjustable or withdrawable auxiliary electrode is so light as to obviate necessity of renewal. except at long intervals.

In Fig. i is illustrated a'well-known form of automatic regulating means for the main electrode C. Such means may comprise a vertically movable electrode-support N,

whose vertical portion is equipped with a rack operated by a pinion N attached to a worm-wheel N actuated by a worm N on the shaft of an electric motor N. The motor is controlled by a circuit (notshown) in the usual manner, which operates to maintain the proper are at the main electrode, according to the current flowing in the main circuit.

In Fig. 5, manual adjusting means for the-auxiliary electrode D' is shown. Such means may be like that shown in Fig. 4, except that the motor and its automatic controlling means may be omitted. The elements in Fig. 5 which correspond with similar elements in Fig. t are correspondingly lettered. In this case, however, the shaft equipped with the worm N is operated by a bevel-gear N actuated'by a bevel-pinion on a shaft equipped with a hand-wheel N Similar manual means may be employed as an auxiliary adjusting means in connection with the mechanism shown in Fig. 4, if desired.

Fig. 2 represents the preferred form of a two-phase furnace embodying the invention. A represents the fusing-chamber; B, B two wall-contacts embedded in the refractory hearth and substantially insulated from each other; C, C two automatically regulated upper main electrodes; D, a manually adjustable or withdrawable auxiliary electrode; E, the primary windings of a twophase transformer or transformers so connected as to deliver a two-phase secondary current, the primary current being a threephase alternating current, if desired; F, F the secondary windings of the transformer device; G, a conductor connecting one terminal of one secondary phase to the main electrode 0 H, a conductor connecting the other side Or terminal of the same secondary phase to the wall-contact B; G a conductor connecting one terminal of the other secondary phase to the main electrode O H and H conductors connecting the other terminal of the last-mentioned secondary phase to the Wall-contact B and the auxiliary electrode, respectively; and H a conductor equipped with a switch H and connecting the conductor H, to the conductor H thus bridging the space between the wall-contacts B and B during the preliminary heating operation. The effect is to connect the conductor H both to the wall-contact B and the auxiliary electrode D, so that the latter will serve as acommon return for both secondary circuits during the operation of preliminarily heating the furnace to render the refractory facings 1 and 1 conductive. It may be noted here that the wall-contacts are of large area so that the current spreads in passing from the main electrodes to the hearth. Moreover, it will be observed that the currents of the two secondary circuits cross in the charge M when the main circuits are established, as indicated by the dotted diagonal lines in Fig. 2.

In this case, also, it is preferred to maintain the auxiliary electrode D in close contact with the charge M and establish arcs at 2, the current passing through the charge to the auxiliary electrode D, during the preliminary heating operation. When the hearth becomes sufliciently conductive to carry the load, the switch H is opened and the auxiliary electrode D is withdrawn from operation.

The main electrodes C and C are preferably equi ped with automatic regulating means of the character illustrated in Fig. 4; and the auxiliary electrode D is preferably equipped with manual adjusting means of the character shown in Fig. 5.

Fig. 3 represents the preferred form of a tri-phase furnace embodying the invention. A represents the fusing-chamber; B a wall-contact embedded in the hearth; C C, C automatically regulated main electrodes; D a manually adjustable auxiliary electrode; E the primary winding of a transformer device adapted to deliver a threephase current; F F, F, the secondary windings of. the transformer or suitably connected transformers; G ,.G, G conductors connecting one terminal of the three secondary phases to the main electrodes C C and C respectively; and H, H conductors connecting the other terminal of said phases to the wall, or hearth contact, B and auxiliary electrode D respectively.

The main electrodes may be provided with automatic regulating means of the character shown in Fig. 4; and the auxiliary electrode D may be provided with the manual regulating means shown in Fig. 5. The transformer device may comprise a threephase transformer, or a series of transformers so connected as to deliver a threephase secondary current. In preliminarily heating the furnace, it is preferred to adjust the auxiliary electrode D in contact with the charge M, and to so adjust the main electrodes C C and C as to. establish arcs 2. In reliminarily heating the furnace, the anxlliary electrode D serves a a common return for the current from the three main electrodes. When the furnace becomes hot, the refractory facing 1 of the wall-contact I becomes sufficiently conductive to carry the load, whereupon the auxiliary electrode 'D is preferably withdrawn from operation.

The main upper electrodes ordinarily are composed chiefly of carbon, but any suitable material may be used; and any suitable lower main electrode or wall-contact may be employed. In the illustrations given, an

iron or steel grid having a carbonaceous block molded thereon is employed. The metal bars may extend to a water-cooled shank, or bar, to which the conductors may be attached. as indicated diagrammatically in Fig. '2. So, also, any suitable forms of electrode supporting and adjusting devices may be employed. Preferably, an alternating secondary current is employed for operating the furnace, but the invention is not to be considered as unnecessarily limited. So. also. it is preferred to operate with the auxiliary electrode in contact with the furnace charge during the preliminary heating of the furnace. thus avoiding arcing at the auxiliary electrode. Obviously, however. the invention is not limited to such mode of operation.

The improved furnace is of the greatest simplicity consistent with stabilized operation, is eflicient in operation, and is capable of being placed in operation with the greatest facility. These advantages and other advantages possessed by the furnace will be readily appreciated by those skilled in the art.

The invention is applicable not only to the single-phase. two-phase and tri-phase systerms. but also to any multi-phase system which it may be desirable to employ in furnace construction. The use of the invention obviates certain objections inherent in electric furnaces employing main electrodes of opposite polarity in the upper portion of the heating chamber for carrying on the normal operation of the furnace; and possesses decided advantages over the induction type of furnace. The invention renders unnecessary the use of heating resistances in the furnace-walls and special circuits therefor, for the purpose of preliminarily heating the furnace.

The foregoing detailed description has been givenfor clearness of" understanding only, and no unnecessary limitation should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

\Vhat I regard as new, and desire to secure by Letters Patent, is:

1. In an electric furnace, the combination of a heating chamber provided with a wall terminal. a co-acting main electrode of opposite polarity, and an auxiliary electrode of the same polarity as said wall terminal and adapted to serve in preliminarily heating the furnace.

2. In an electric furnace, the combination of a heating chamber having a wall terminal with a refractory facing which is conductive when hot. a co-acting main electrode of opposite polarity adapted to arc at the upper portion of the charge. and an auxiliary electrode of the same polarity as said wall terminal and adapted to contact with the upper portion of the charge and co-act with said main electrode in preliminarily heating the furnace.

3. In an electric furnace, the combination of a heating chamber having a wall terminal with a refractory facing which is conductive when hot, a co-acting main electrode of opposite polarity adapted to are at the upper portion of the charge. a withdrawable auxil iary electrode extending into the heating chamber near the upper portion of the charge, and a transformer having a secondary circuit with one terminal connected with said main electrode and another terminal connected with both said wall terminal and auxiliary electrode.

i. In n electric furnace, the combination of a heating chamber having a hearth provided with an embedded terminal faced with refractory material which is conductive when hot, said chamber having a top wall provided with openings, a main electrode de-- pending through one of said openings and adapted to operate an are at the upper portion of the charge, an auxiliary electrode depending through another opening in the top wall and adapted for ready withdrawal, and a transformer having a secondary circuit with one terminal joined to said main elec trode and another terminal joined to both said wall terminal and said auxiliary electrode.

5. Inan electric furnace, the combination of a heating chamber having a lower terminal, an upper main electrode equipped with automatic adjusting means, areadily withdrawable auxiliary upper electrode, and a transformer having a secondary circuit with one terminal joined to said main electrode and another terminal joined both to said lower terminal and said auxiliary electrode.

6. In a. poly-phase electric furnace, the combination of a heating chamber having a. hearth equipped with terminal means provided with a refractory facing which is conductive when hot, a plurality of upper main electrodes, an upper auxiliary electrode adapted to form a common return for the current from the main electrodes in preliminarily heating the furnace, and transformer means whose secondary circuits are connected on one side to said main electrodes and on the other side to said bottom terminal means and said auxiliary electrode.

7. The method of electric furnace operation which consists in using an auxiliary electrode in conjunction with the main elec-' trode for heating the furnace and making the wall-contact sufficiently conductive and then using said main electrode and said wallcontact to carry on the operation of the furnace.

8. The method of operating an electric furnace having a wall-contact or contacts with a refractory facing and an arcing main electrode or electrodes adapted to coact therewith when the furnace is hot, which consists in preliminarily heating the furnace by passing current through the charge in the furnace between said electrode or electrodes and an auxiliary electrode which serves as a pole in lieu of said wall-contact till the wallcontact becomes sufliciently conductive to carry the load, and thereupon withdrawing the auxiliary electrode from operation and causing the current to be carried wholly through the charge to the furnace-wall and to the wall-contact or contacts.

9. In an electric furnace, the combination 15 of a heating chamber provided with a wall terminal, a co-acting upper main electrode of opposite polarity, and an auxiliary electrode of the same polarity as the wall terminal, equipped with mechanical adjusting 2 WILLIAM K. BOOTH. 

